The main feature of a logarithmic amplifiers is its non-linear transfer characteristic. This type of amplifier expands the dynamic range of small input signals and compresses that of large input signals. A common problem with integrated logarithmic amplifiers is that they saturate very easily. This is due to the fact that they amplify their own input offset voltages. Because of the very large gain in the small signal range, even a small input offset voltage creates a large output signal, thus reducing the available dynamic range for the input. Therefore, it is often necessary to compensate for the input offset voltage.
A conventional approach is to use resistor trimming to cancel the input offset voltage of the amplifier. However, resistor trimming is an expensive procedure. Furthermore, this technique is static. Although it can compensate for input offset voltages caused by process variations, it can only cancel the input offset voltage at the temperature at which trimming was performed. As a consequence, this resistor trimming technique does not compensate for changes in the input offset voltage as a result of changes in the temperature of the integrated circuit.